Integrated biological-physical process for biogas purification effluent treatment

Area of Science:

• Environmental Engineering
• Biotechnology
• Chemical Engineering

Background:

• Biogas purification effluent contains methane (CH4), hydrogen sulfide (H2S), and carbon dioxide (CO2).
• These components contribute to greenhouse gas emissions and hinder water regeneration.
• Effective treatment is crucial for environmental protection and resource recovery.

Purpose of the Study:

• To develop and evaluate a reactor system for treating biogas purification effluent.
• To optimize CH4 removal, H2S elimination, and CO2 stripping.
• To assess the impact of airflow rates and hydraulic retention time on treatment efficiency.

Main Methods:

• Utilized a reactor with dual air supplies (top and bottom) for biological oxidation and physical stripping.
• Investigated varying upper and bottom airflow rates and hydraulic retention times.
• Performed microbiological analysis to identify key microbial communities.
• Developed a mathematical model to predict performance.

Main Results:

• Achieved up to 98% CH4 removal at a 2-hour hydraulic retention time and 2.02 L/day upper airflow.
• Completely removed H2S, with minimal CH4 (0.04%) in off-gas, and observed sulfur precipitation.
• Identified optimal upper airflow rate and a 50 L/day bottom airflow rate for efficient CO2 stripping and pH adjustment (5.64 to 7.3).
• Confirmed dominance of Methylobacter and Methylocaldum (methanotrophs) and Hyphomicrobium (sulfide-oxidizing bacteria).

Conclusions:

• The combined biological and physical treatment effectively removes CH4 and H2S from biogas purification effluent.
• Optimized airflow rates are critical for efficient CO2 stripping and effluent pH neutralization.
• The identified microbial communities play a vital role in the treatment process, enabling methane and sulfide oxidation.